How to test preferred color scheme (Dark Mode) with Firefox

Hi, I’m the author of the previously mentioned extension.
First of all, great to see the extension is useful for you!

However, due to a missing API in Firefox, the manipulation is indeed more of a workaround in a hackish way and certainly not a good way. This is also stated in various places, so read the Readme for a more detailed explanation. The API Bugzilla request is here in case you want to upvote it.


Apart from all that recent Firefox versions, however have introduced a feature for developers so you can change the style in dev-tools. Just enable the option devtools.inspector.color-scheme-simulation.enabled and then you can find this button:

There was also a preference ui.systemUsesDarkTheme for globally forcing the dark style, but somehow that did not work for me in Firefox 83.

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